This invention relates generally to optical lens systems, and, more particularly, relates to stereoscopic objective lens designs adapted for use in stereo video telescopes.
Medical endoscopes are a form of telescope which is widely utilized to view internal regions of the human body during diagnostic, surgical, and other medical procedures. Endoscopes typically include a long, thin, rigid or semi-rigid optical cylinder affixed to a viewing mechanism. The cylinder is sufficiently narrow to be inserted through a small opening in the body, which may be natural or surgical. When the endoscope is inserted and positioned for use, an image of the object being viewed is formed at an inserted end of the endoscope by an objective lens. The image passes through a series of relay lenses down the cylinder to an eye lens or video camera at a viewing end of the endoscope.
In recent years, researchers have attempted to improve the imaging available through endoscopic devices by developing stereoscopic video endoscopes. These endoscopes present an apparently three-dimensional image on a video monitor. The stereoscopic effect is created by producing two optical images--a left image and a right image--through the endoscope. The left and right optical images are presented by the endoscope to left and right image sensors, which may be charge-coupled device (CCD) cameras or other image sensing devices. The sensing devices convert the left and right optical images into left and right video images which are then presented as alternating left/right images on a monitor, at a switching rate higher than the flicker-sensing limit of the human eye, so that observed images appear flicker-free.
The images are alternately switched from a left-hand polarization mode to a right-hand polarization mode, such that, for example, the left image has a left-hand polarization and the right image has a right-hand polarization. In accord with this example, the observer wears polarized glasses in which the left lens has the left-hand polarization and the right lens has the right-hand polarization. Thus, the left eye sees only images from the left channel of the endoscope system and the right eye sees only images from the right channel, resulting in stereoscopic viewing.
The following United States and foreign patents disclose examples of stereo endoscopes, some of which utilize video imaging and display elements:
U.S. Pat. No. 4,061,135 PA1 U.S. Pat. No. 4,615,332 PA1 U.S. Pat. No. 4,651,201 PA1 U.S. Pat. No. 4,862,873 PA1 U.S. Pat. No. 4,873,572 PA1 U.S. Pat. No. 4,895,431 PA1 U.S. Pat. No. 5,122,650 PA1 U.S. Pat. No. 5,191,203 PA1 U.S. Pat. No. 5,673,147 PA1 EP Patent No. 211,783
In particular, U.S. Pat. No. 4,061,135 discloses a binocular endoscope in which images are transmitted from the viewed object to the viewing station through an optical system utilizing a dove prism and mechanical linkage to compensate for rotation effects.
U.S. Pat. No. 4,615,332 discloses a binocular endoscope having flexible light guides and binocular eyepieces.
U.S. Pat. No. 4,651,201 discloses a stereoscopic video endoscope including two image guides and an illumination light guide. The image guides are optically coupled to a stereoscopic viewer for three dimensional viewing. The viewer includes couplings for attaching miniature video camera that can be connected to a head mounted stereoscopic video display.
U.S. Pat. No. 4,862,873 discloses a stereo endoscope having two light guides for carrying images of an object an electro-optical imaging assembly. A lens system directs light from the object to the objective end of the light guides. Illuminating light is transmitted to the object from the opposite end of one light guide, thereby illuminating the object. Simultaneously, the image transmitted through the other optical guide is conducted to the imaging assembly.
U.S. Pat. No. 4,873,572 discloses a stereo endoscope having a CCD camera module and two image-forming lens systems that form two object images. The object images are integrated and directed to the CCD camera to provide a stereoscopic output. The lens systems include red, green, and blue color filters disposed at the camera imaging surface.
U.S. Pat. No. 4,895,431 discloses an endoscope apparatus that generates a three-dimensional image of an object from overlapping images recorded by a camera. The endoscope includes an insertion module and a movable end section capable of being deflected through an angle. A first image is recorded with the end section positioned at a first angle. A second image, partially overlapping the first image, is recorded after moving the end section to a second angle. The relative position of the movable end section is detected by an encoder that generates position signals for input to a microprocessor, which utilizes the position signals to generate a three-dimensional image of the object.
U.S. Pat. No. 5,122,650 discloses a stereo video endoscope objective lens system using six doublet lenses to generate pixel mapped left-right images for stereo viewing.
U.S. Pat. No. 5,191,203 discloses a stereo video endoscope objective lens system using lenses having a graded index of refraction to generate pixel mapped left-right images for stereo viewing.
U.S. Pat. No. 5,673,147 discloses a stereo video endoscope objective lens system which uses ball lenses for the left and right stereo lens pair.
European Patent No. 211,783 discloses a stereo video endoscope in which two light pipes deliver two images of the same object. These images are presented by a binocular device to the user's eyes to show a three dimensional image of the target. The apparatus includes two television cameras and video recorders for recording the images. The recorded images can be displayed on separate screens and viewed by a binocular viewing system.
Most conventional stereo endoscopes, however, share a number of deficiencies associated with their objective lens systems. These problems include a bulky and unwieldy configuration; high cost and complexity of fabricating the objective lens system; and the less than optimal optical performance afforded by conventional objective lens systems.
An additional problem associated with conventional stereo video endoscope objectives involves the requirement that all portions of each left/right image be mapped to within a fraction of a video pixel to each other. This pixel mapping condition is a significant optical design constraint, because the object-to-image ray paths through the lens system are quite different for the left and right image points associated with a common object point.
A further problem is the general characteristic of conventional endoscopes that the magnification is fixed for each such instrument. The present invention is directed to the latter problem.
Accordingly, it is a general object of the present invention to provide improved stereo telescope objective lens systems that selectively provides multiple magnifications.
A more specific object is to provide an improved stereo telescope objective lens system having optical elements that may be selectively placed in the optical train to provide different magnifications.
The above and other objects and advantages of this invention will become more readily apparent when the following description is read in conjunction with the accompanying drawings.